Survivin expression pattern in the intestine of normoxic and ischemic rats

Abstract

Background: Survivin, a member of the inhibitor of apoptosis protein (IAP) family, regulates mitosis and chromosome segregation. The expression of survivin proceeds during embryonic development and in addition has already been demonstrated in cancer cells. However, there is also evidence of survivin expression in differentiated tissues, including the gastro-intestinal tract of adult rats. A study with human colon specimens exhibited survivin in most basal crypt epithelial cells of normal mucosa. There is rather limited information on survivin expression in the small intestine. In order to paint a more detailed and thus complete picture of survivin expression patterns in the gastrointestinal tract, we used an immunohistochemical approach in normal adult rat small intestinal and ascending colonic tissue. Moreover, to get deeper insights in the regulation of survivin expression after tissue damage, we also studied its expression in mesenteric ischemia-reperfusion (I/R) injury.

Methods: Mesenteric ischemia-reperfusion injury was induced in male Wistar rats (six animals/group) by occlusion of the superior mesenteric artery for 90 min and subsequent reperfusion for 120 min. Paraffin sections of untreated or ischemically treated tissue were assessed immunohistochemically by survivin and Ki-67 staining.

Results: Survivin could be detected in the small intestine and ascending colon of the normoxia group. It was expressed mainly in the epithelial cells of the crypts and only marginally in the villi. The individual small intestinal segments studied revealed comparable staining intensities. Likewise, expression of survivin was detected in the ischemically damaged small intestine and ascending colon. The expression pattern corresponded to the normoxic animals, as far as verifiable due to the existing tissue damage. Comparison of the expression pattern of Ki-67, a protein that acts as a cellular marker for proliferation, and survivin demonstrated a coincidental localization of the two proteins in the small intestinal and ascending colonic tissue.

Conclusions: Survivin was expressed strongly in epithelial cells of small intestinal as well as ascending colonic tissue. Its expression was located in cells with a high proliferation rate and regenerative capacity. This further supports the decisive role of survivin in cell division. Surprisingly, the ischemically damaged small intestinal and ascending colonic tissue showed a comparably high expression level. These results suggest that there is already a maximal survivin expression under normal conditions. However, the intestine is able to maintain the regenerative capacity even in spite of an ischemic injury. These findings reflect the important relevance of an intact intestinal barrier.

Keywords: Immunohistochemistry; Injury; Intestine; Ischemia; Rat; Reperfusion; Survivin expression.

Fig. 1

Survivin expression in the normoxia group. a Survivin staining of intestinal segment III in the normoxia group (representative figure). Survivin positive cells were immunohistochemically labeled in brown. (I): single crypt; (II): small intestine (jejunum). Nuclei were stained blue by hematoxylin counterstaining. Magnification: 400×. Scale bar: 10 μm. b Percentage of survivin expression. The results revealed no significant difference. Values are means ± standard error of the mean (n = 6). c Ki-67 positive cells were immunohistochemically labeled in brown. Nuclei were counterstaining with hematoxylin (blue). Magnification: 400×. Scale bar: 10 μm. d Percentage of Ki-67 expression. The results revealed no significant difference. Values are means ± standard error of the mean (n = 6)

Fig. 2

Survivin expression in the ischemia group. a Survivin staining of intestinal segment VII in the ischemia group (representative figure). Survivin positive cells were immunohistochemically labeled in brown. (I): single crypt; (II): small intestine (ileum). Nuclei were stained blue by counterstaining with hematoxylin. Magnification: 400×. Scale bar: 10 μm (b) Percentage of survivin expression. Values are means ± standard error of the mean (n = 6). c Ki-67 positive cells were immunohistochemically labeled in brown. Nuclei were counterstaining with hematoxylin (blue). Magnification: 400×. Scale bar: 10 μm. d Percentage of survivin expression. Values are means ± standard error of the mean (n = 6)

Fig. 3

Survivin and Ki-67 staining in the ascending colon. (A/B) Survivin staining of the ascending colon in the normoxia (a) and the ischemia (b) group (representative figures). Survivin positive cells were immunohistochemically labeled in brown. (I): single crypt; (II): ascending colon. Nuclei were counterstaining with hematoxylin (blue). Magnification: 400×. Scale bar: 10 μm. (C/D) Ki-67 staining of the ascending colon in the normoxia (c) and the ischemia (d) group (representative figures). Ki-67 positive cells were immunohistochemically labeled in brown. Nuclei were counterstaining with hematoxylin (blue). Magnification: 400×. Scale bar: 10 μm